Process for making grinding surfaces for charge containers



A 1 5 H. H. WOLFF PROCESS FOR MAKING GRINDING SURFACES FOR CHARGE CONTAINERS Filed Ju1y 29, 1941 Fig.1. 0 7 A5 6 4 6 E 4 8 Inveni/or:

flads llormann 7V2) a material with the material Patented Aug 7, '1945 3:4;

" frnocnss m me GRINDING stm- FAG ES FOB-EGHARGEEONTAINERS- fHans Hermann Wolff, Stockholm,- Sweden/as *sign'or' {to Aktiebolaget' Hammarbylampan, Stockholm, Swedern a company of Sweden a Claims... (Cl. air -30) This invention relatesto a processfor making. a' hard lining f for asurfa'ce of acharge container forgrinding hardmaterial. I

To illustrate theinvention, the accompanying drawingshows by way ofexampl'e a mill. accordingto the invention, wherein:

Fig; 1" shows a longitudinal section. offatmill container for grinding. hard alloy constituents. and.

having a grinding: surface according to the .in-

Ventionjand Y f Fig. "2 illustrates diagrammatically one. form of the driving mechani'sm forthe-milll. v

The mill. consists of' a. cylindrical container 4,

of copper which is closed. by. a-wall 2'. at one, of its ends and. by a removable cover or lid. 9.v at the Qther; open end 3' The' cover 9 may secured to the. ange 6 offthe containerf4by means of bolts. 8or.equivalent.meniber's, The interior wall of the mill container hasa grinding surface 5. of. hard. metal,-z produced in. the manner described above, i. 'e.,. by pressing the" pulverulent. hard alloy into the soft copper Wall, for instance-during a preparatory operation. of. grinding. t

. When it. is desired to use the millior. grinding. hard. alloy constituents the said constituents (m1 a 'pul'verulent state) together with a grinding liq.- uidsuch-es. methylene chlorine or the like. are

introduced into-the container throughtheopen-- ing.. 3 (the. cover fixbei'n g removed) and inthe same. manner also suitablegrinding bodies l such as roundedv or cylindrical or otherwise shaped pieces cit-hard metal are introduced into the container 4.. the cover 9 is securedto the I flanges 6, preferably through theint'ermediaryof a packing'ring ,1. The container is. now caused. to rotate; tor, instance by rotating the rollers l from, a suitable source of Bow n. resulting. in the.

. It is exceedingly importantthat the hard al-l loys, which generally'have a composition very;

obtained so astoimpairthe same. Furthermore.)

generally the special steels; madeuse oflafeex pensive and v'ery hardtowork by. reason. of.

. which the method. in. question will befound. to. be

fer-m mas of a hard. not abrasible lining,l,rigid" enough to withstand, abrasion] to, a. high. extent during the grinding operations] For the production of hard. alloys it is. necessary that the constituents.bebrought. into=a very finely d'ivided state prior to the sinteringoperatibn. This finefdivisiongof the material is. generally eiTected through grinding in. aballmill. Since. the constituents oi hard alloys sub stantially consist of very hard materials, such.

as carbides, a .very long grinding time 'is ordinarily.reduiredsso' asto obtain the desired degree of fineness of the material. The long grinding time in connection with the hard ma-' terial, however, results in wear of the mill sur face and the mixture of the charge container wall to be ground becomes too great.

rather'expensive- According. to another method; v

amaterial which is one of the. constituents of the. material to be ground has been used asa. mill material. In this case, no direct impurities caused bywearwillbe. introduced. intothe grindgoods but on. theother handa.v factor of un.-. certainty .willi arise on. account. of the fact. that. the quantity of. worn-01f material may vary from time to. time, so that. the uniformity in the. qual- I ity will sufferl... Itis true that. the grinding bodiesor ballsmade fromhard alloys of the same com position. asthat ct thematerial to, bev ground is.

conceivablabut when attempts are made toimaljre. the mill or mill charge container liningjitsel't.

from. the said material practical and economic? difiicultiesl arise. I I The main object of the presentinventionis to.

provide a metho.d,. according to which practically" the same result is obtained as if the. mill. C011", sistedof hard..metal, Accordingto the inven.-- tion. there-is. used-a mill provided with agrinding surface for thecharge container consisting of; one or more layers 'ofifinely divided. hard mate rial rigidly attached to the internal walls. of the mill. a Y

A further objectof' the invention is to-produce the said layer in an. exceedingly simple. manner by making the housing or. internal walls of. the. mill from. a sottmaterial, such as copper, which: is adaptedto receive the finely divided hard ma.- teriaL;so..that.-such.material. is caused to. penetrate and adhere rigidly to the said soft mate rial as a lining. It has been established that if one or a few preparatory grindings of hard material be effected in a mill of this kind, some of the hard metal powder or splinters will penetrate into the soft material and stick thereto, so that the whole surface of the mill container gradually will be covered thereby as by a protecting jacket.

One could believe that where a material as soft as copper is selected, the wear would still be very great, and that the percentage of copper in the material ground would be found to be too high upon termination of the grinding operation. In contradistinction to what could be expetced, however, the copper percentage will be so low after i a. few grinding operations, even with the use of grinding material of hard metal, that it may be disregarded entirely. The table hereinbelow shows the copper percentage obtained in the ground material after the first four grinding'opheating it on or in a suitable substance, whereupon the material thus obtained is used as a mill lining.

As many changes could be made in the above construction and many apparently widely different embodiments of the invention could be made without departing from the scope thereof, as defined by .the following claims, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What I claim is: 1. That process of making a hard lining for the 3 internal surface of a charge container of a mill for thereafter grinding hard material that may be used in carrying out a sintering or like methd, which process of making the lining comprises As will be seen, the copper percentage dimin ishes very rapidly, and after the fourth grinding operation it constitutes only about a tenth of the copper percentage obtained after the first grind-' vary, but in its simplest embodiment it is constituted of a cylindrical container 4 provided with a cover 9 adapted to be secured thereon with a tightfit by means of a suitable securing means such as a screw device 8 and gasket 1. If the mill be made from copper in its entirety, it may be found suitable to reinforce the sameexternally by rings 3-6 from some material resistant to wear. With theserings the mill may roll on the rollers 10 generally provided in the operation of mills of this kind. The rings may be made from iron, and, if desired, they may be covered with rubber.

It is also not necessary to make the whole mill from copper, the substantial point being that the internal walls |2 of the same are constituted of or coated with copper 5. This may be effected by'internally coating an iron vessel or the like with copper by electroplating.

According to the method set forth above the hard metal layer is applied only after the remainder of the mill has been manufactured. Although this method is believed to be the simplest and most suitable, there is no objection to making a special lining layer which then is attached to the mill. Thus, the finely divided hard metal layer may be applied by pressing or,

the following steps; providing for the mill a grinding wall of copper which is essentially softer than saidhard material; placing in the container provided with such wall a sufficient quantity of the saidhard material for the making of preparatory grindings; then making such preparatory grindings in the presence of usual grinding bodies as employed in ball-mill grinding operations, and therebyreducing such hard material of said preparatory grindings into fine particlesand mechanically pressing them by said preparatory grindings into the substance of said copper wall, so as to cause such fine particles to penetrate and adhere thereto, and thus provide for said copper wall .a protecting jacket of one or more layers of finely divided hard material rigidly attached to the said internal copper wall of the mill container, whereby a grinding surface is provided for the containenin which container, there may be gI'OLlIId into powdered form other quantities of such hard material for use in a sintering or like method.

2. That process of making a hard lining for the internal surface of a charge container of a mill for thereafter grinding hard material that may be used with a suitable binding agent in powdered form in carrying out a sintering or like method, which process of making the lining comprises the following steps; providing for the mill a grindingwall of copper which is essentially softer than said hard material; placing in the container provided with such wall a sufficient quantity of the said hard material for the making of a few preparatory grindings; then making such few preparatory grindings in the presence of usual grinding bodies as employed in ball-mill grinding operations, and thereby reducing such hard material of said few preparatory grindings into fine particles and mechanically pressing them by said few preparatory grindings into the substance of said copper wall, so asto cause such fine particles to penetrate and adhere thereto, and thus provide for said copper wall a protecting jacket of one or'more layers of finely divided hard material rigidly attached to the said internal copper wall of the mill container, whereby a grinding surface is provided for the container, in which container there may be ground into powdered form other quantities of such hard material for use in a sintering or like method.

HANS HERMANN WOLFE. 

